I can organise tours to Holy Mount Kailash. Allow at least 8 days to get
acclimatised and another 8 days to do the circumambulation (including transfers).
Even with an experienced guide you have be in a pretty good shape to consider
this pilgrimage. Passes to be crossed go up to 5,600 m.

You can start off from Kathmandu or Lasha and add sightseeing either in
Tibet or in Nepal.